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foreword	milestones	version 2	version 2	(background - core - applications)	library	(static LDDL directory)
citations	visibility	version 1	version 1	(static HELM directory)	helena

Informal description: ""

{λ[a:Prop] .​ λ[b:Prop] .​ λ[a1:a] .​ λ[n:(b) .​ not ]} .​ <({(b) .​ (a)} .​ iff ) .​ not > .​ {({(n) .​ (a1) .​ (b) .​ (a)} .​ th4 ) .​ ({(a) .​ (b)} .​ imp ) .​ ({(b) .​ (a)} .​ imp )} .​ th1

Validation parameters: sort hierarchy = "Z2", kernel options = ""